I also assumed that the study population was fully susceptible initially, whereas there is evidence of variable susceptibility to social contagion [1]}, [2]}. However, if infectious individuals only nominate others who would be in the susceptible group at the start of the outbreak, then transmission should not be affected by the presence of non-initially susceptible individuals, as they will not form part of a potential nomination chain. In addition, I did not include potential for spatial synchrony as a result of nominations occurring across different regions. The second peak for NKN in Australia, which coincidences with the main outbreak in the UK (Figure 1), may be the result of such cross-continent nominations. Without detailed data on between-region transmission chains, however, it would be difficult to justify a more complex model, and I therefore chose to focus on a simple SIR framework in the analysis.
